I really like the animations, makes it intuitive to understand what is happening!
One disadvantage that I think parser combinators have, for example compared to parser generator libraries (where the parser is generated from a seperate grammar file), is that you have to add a lot of mapping / unwrapping code. In my opinion this makes the parsers harder to read.
As an attempt to improve this, I have been working on a parser combinator library in rust. It adds two extra combinators (capture and bind) which can store the results of parsers in buckets (bind) and use the values stored in these buckets later to construct results (capture). This allows you to eliminate the unwrapping / mapping code and seperate the grammar from the result contstruction.
If you have the time, I would really appreciate feedback on this!
You can find it here: https://github.com/ArneCode/marser